The invention concerns a device for adjusting a chuck to axially tension core tubes and consisting of a driven spindle and of a spindle nut that can be displaced by the spindle and is attached to the chuck.
Several adjusting devices of this type are mounted on spiders that support the reels in a known unwinder. The chuck, which has a conical shell for example, moves back and forth axially along a rail in relation to the core tube. The spindle is driven by a motor and an angled transmission. The force with which the expanding-core chuck that travels axially into the core tube can be adjusted, cannot be precisely prescribed in an unwinder of this type, and, if that force is too powerful, the resulting radial force may be strong enough to tear the cores, which can no longer be used.